A lubricating oil composition for an internal combustion engine contains: a base oil having a viscosity index of 120 or more; and a polymer compound that includes a first constituent having a mass average molecular weight of less than 100,000 and a second constituent having a mass average molecular weight of 100,000 or more, the first constituent of 0.01 mass % to 10 mass % being contained relative to a total amount of the lubricating oil composition, preferably 0.1 mass % to 10 mass %, the second constituent of less than 0.5 mass % being contained relative to the total amount of the lubricating oil composition. A viscosity index of the lubricating oil composition is 130 or more.